The influence of inconsistent handling by humans on the behaviour, growth and corticosteroids of young pigs
The influence of 4 handling treatments on the behaviour, growth and free corticosteroid concentrations were studied in 32 young female pigs housed in individual pens. The pleasant treatment involved stroking the pig whenever it approached the experimenter, the unpleasant treatment involved forcing the pig away whenever it approached the experimenter and the inconsistent treatment was a combination of unpleasant and pleasant treatments (imposed at a ratio of 1:5). These 3 treatments were imposed for 3 min each, 3 times per week, from 7 to 13 weeks of age. The fourth treatment, minimal handling, involved minimal contact with humans during this 6-week period. Gilts in the pleasant and minimal handling treatments had higher (P < 0.05) growth rates and feed conversion efficiencies over the first 2 weeks of the study than gilts in the unpleasant and inconsistent handling treatments. The gilts in the unpleasant and inconsistent handling treatments had higher (P < 0.01) free corticosteroid concentrations in the absence of humans at 14 weeks of age and were more (P < 0.05) fearful of humans, as indicated by less approach to a stationary human, at 14 weeks of age than gilts in the pleasant and minimal handling treatments. It was concluded that the unpleasant and inconsistent handling treatments resulted in a chronic stress response with consequent adverse effects on growth performance. The implications of these results for the reproductive performance and welfare status of breeding pigs are discussed.